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Foundations in

MicrobiologySixth Edition

Chapter 2

The Chemistry ofBiology

Lecture PowerPoint to accompany

Talaro

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.


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Atoms, Bonds, and Molecules

Matter- all materials that occupy space andhave mass

Matter is composed of atoms.

Atomsimplest form of matter not divisible

into simpler substances

composed of protons, neutrons, andelectrons

Element

pure substances with acharacteristic number of protons, neutrons,and electrons and predictable chemicalbehaviors


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Insert Figure 2.1Models of atomic structure


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Characteristics of Elements

Atomic numbernumber of protonsMass numbernumber of protons and neutrons

Isotopesvariant forms of an element that differ in

mass number

Atomic weightaverage of the mass numbers of

all of the elements isotopic forms

Electron orbitalsvolumes of space surrounding

the atomic nucleus where electrons are likely to befound


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Insert figure 2.2Periodic table


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Molecules and Bonds

Moleculedistinct chemical substance thatresults from the combination of two or more atoms

Compoundsmolecules that are combinationsof 2 or more different elements

Chemical bondswhen 2 or more atoms share,donate or accept electrons to form molecules andcompounds

3 types: covalent, ionic, and hydrogen


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3 Types of Chemical Bonds

1. Covalent bondselectrons are sharedamong atoms

polarcovalent bondsunequal sharing

nonpolarcovalent bondsequal sharing2. Ionic bondselectrons are transferred to

one atom forming positively chargedcationsand negatively charged anions

3. Hydrogen bondsweak bonds betweenhydrogen and other atoms


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Insert Figure 2.33 Types of Chemical Bonds


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Insert figure 2.4Covalent bonds


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Insert figure 2.5H2Oa polar molecule


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Insert figure 2.7

Ionization


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Insert figure 2.8

H-bonding in H2O


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Electron Transfer and Oxidation-

Reduction Reactions

Energy exchanges in cells is a result of the

movement of electrons from one molecule to

another.

Oxidationthe loss of electrons

Reductionthe gaining of electrons

Redox reactionsessential to biochemical

processes


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Insert figure 2.9

Redox reaction


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Solutions: Mixtures of Molecules

Solutes

Na+& Cl-

SolventH2O

Insert figure 2.7ionization

Solutiona mixture of one or more substancescalled solutes, dispersed in a dissolving medium

called a solvent


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Most biological activities occur inaqueous(water-based) solutions.

Hydrophilic moleculesdissolve in water

Hydrophobic moleculesrepel water Amphipathic molecules -have both

hydrophilic and hydrophobic properties


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Insert figure 2.12

Ions in solution


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Acidity, Alkalinity, and the pH

Scale

Ionization of H2O releases hydrogen ions[H+] and hydroxyl ions [OH

-]

pH scaleranges from 0 to 14,expresses the concentration of H+ions

pH is the negative logarithm of theconcentration of H+ ions.

pH 6 = 0.000001 moles H+/ l

pH 9 = 0.000000001 moles H+/ l


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Insert figure 2.13

pH scale


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The Chemistry of Carbon and Organic

Compounds

Organic chemicalscompounds

containing both carbon and hydrogen

atoms


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Carbon is the fundamental element of life contains 4 atoms in its outer orbital

can form single, double, or triple covalent

bonds can form linear, branched, or ringed molecules


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Insert figure 2.14Carbon bonding


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4 Families of Macromolecules

1. Carbohydratesmonosaccharides,disaccharides, polysaccharides

2. Lipidstriglycerides (fats and oils),phospholipids, steroids

3. Proteins4. Nucleic acidsDNA, RNA

5. Except for lipids, all are formed by polymerization,6. where subunits, called monomers,are bound into

7. chains called polymers.


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Insert figure 2.15Carbohydrates


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Lipids

Long or complex, hydrophobic, C - Hchains

Triglycerides, phospholipids in

membranes, steroids like cholesterol Functions

triglyceridesenergy storage

phospholipidmajor cell membranecomponent

steroidscell membrane component


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Insert figure 2.18triglycerides


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Insert figure 2.19

phospholipids


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Insert figure 2.20

Cell membrane


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Proteins

Predominant molecules in cells

Monomeramino acids20

Polymerpeptide, polypeptide, protein

Subunits linked by peptide bonds

Fold into very specific 3-D shapes

Functions - support, enzymes, transport,defense, movement


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Insert figure 2.22Protein structure


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Nucleic Acids

DNA and RNA Monomernucleotide

DNAdeoxyribonucleic acid

A,T,C,Gnitrogen bases double helix

function - hereditary material

RNAribonucleic acidA,U,C,Gnitrogen bases

function - organize protein synthesis


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Insert figure 2.23

Nucleic acid structure


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ATP: The Energy Molecule of Cells

Adenosine triphosphate nucleotide - adenine, ribose, three phosphates

Functiontransfer and storage of energy

Insert figure 2.27 aATP molecule